docs: def set_exe(self, pipes_code):
          """
          Dump launcher code to the distributed file system.
          """
          if not self.output:
              raise RuntimeError("no output directory, can't create launcher")
          parent = hdfs.path.dirname(hdfs.path.abspath(self.output.rstrip("/")))
          self.exe = hdfs.path.join(parent, utils.make_random_str())
          hdfs.dump(pipes_code, self.exe)